1. Statement of the Technical Field
The inventive concepts relate to the design and manufacture of boxes and other types of containers, such as but not limited to multifaceted and fluted containers.
2. Description of Related Art
In U.S. Pat. No. 6,935,997, hereinafter referred to as “the '997 patent,” a method for designing folded sheet structures is described where the corresponding flat unfolded sheet may have a creasing pattern that forms a tessellation on the sheet. The term tessellation refers to a mosaic pattern or other division of a sheet into polygonal or curved regions, or in some cases may refer more specifically to the edges and vertices between the regions in such a division.
Designing folding patterns that have multiple vertices located away from the boundary of a sheet can be difficult. A sheet with one such interior vertex may be produced by conventional methods by having fold creases emanating as rays from the vertex in alternate up-fold/down-fold convexity to yield a coffee-filter like structure. In both the folded and unfolded form the total angle of material surrounding the interior vertex is 360 degrees. To design folding tessellations that have multiple interior vertices is more difficult. Each vertex in the folded three-dimensional form must have emanating fold edges in both convexities, the angles surrounding the vertices must total 360 degrees, and the lengths of the edges between the vertices must be selected to agree trigonometrically with the pleat angles belonging to each of the vertices. In the '997 patent a family of methods for designing folding tessellations is given.
In corrugated materials the corrugations give added bending moment that resists bending across the flutes. This is seen in many materials, including corrugated cardboard, corrugated roofs, and corrugated pipe. In these cases the material has added strength due to the fluted pattern. For generally round shapes, forming the corrugations in the circumferential direction requires the sheet material to be deformed due to the difference in length between the inner and outer radius. This is seen in corrugated pipe, where the sheet material must have enough plasticity to enable the in-plane deformation of the fluting process. For circumferential flutes, as the depth of the flutes increases the required deformation also increases. For paper and other materials with nearly no plasticity, this means that the additional strength resulting from the presence of flutes is not available when a conventional circumferential corrugation methodology is used.